Electrically variable vehicle transmissions (EVTs), such as those described in U.S. Pat. No. 5,931,757, employ two electric motor/generators. The electric motor/generators are coaxially oriented with an input shaft connectable to an engine, an output shaft, and a differential gearing arrangement. Each motor/generator is operatively connected to the differential gearing arrangement to provide a range or mode of transmission operation characterized by a continuously variable speed ratio between the input shaft and the output shaft.
An EVT may be operated in a purely electrical mode wherein the engine is off, or disconnected from the input member, and only the motor/generators supply torque to propel the vehicle. With some EVTs, the motor/generators do not have a reaction member against which to “push” when supplying torque for the output member in reverse mode and with the engine off or disconnected. To compensate, a first motor/generator may provide reverse torque for the output member while a second motor/generator acts on the input member to provide a reaction torque for the first motor/generator. In a powertrain having an engine connected to an electrically variable transmission without an input clutch, the crankshaft is continuously connected to the transmission input member for substantially unitary rotation therewith, and the second motor/generator therefore rotates the crankshaft and motors the engine during purely electrical reverse operation.